In the United States impeachment can occur both at the federal and state level. At the federal level, both the executive branch and the judiciary may be impeached, though different standards apply. For the executive branch, only those who have allegedly committed "reason, bribery, or other high crimes and misdemeanors" may be impeached. Although treason and bribery are obvious, the Constitution is silent on what constitutes a "high crime." Several commentators have suggested that Congress alone may decide for itself what constitutes an impeachable offense.
The standard for impeachment among the judiciary is much broader. Article III of the Constitution states that judges remain in office "during good behavior," implying that Congress may remove a judge for bad behavior.
Though some might semantically refer to it as impeachment, members of Congress only have the authority to discipline and expel their own members - without involving the other chamber, as impeachment would require - and expulsion has become the preferred (albeit rare) method of dealing with errant Members of Congress.
The procedure is in two steps. The House of Representatives must first pass "articles of impeachment" by a simple majority. The articles of impeachment constitute the formal allegations. Upon their passage, the defendant has been "impeached."
Next, the Senate tries the accused. In the case of the impeachment of a President, the Chief Justice of the United States presides over the proceedings. Otherwise, the Vice President, in his capacity of President of the Senate, or the President pro tempore of the Senate presides. This would include the impeachment of the Vice President.
In order to convict the accused, a two-thirds majority of the senators present is required. In the case of current office-holders, conviction automatically removes the defendant from office. Following conviction, the Senate may vote to further punish the individual...